In an operating machine such as a mini shovel, a swash plate type piston pump is driven by an engine. A hydraulic actuator performing various operations is driven by working oil discharged from the piston pump. Power of the swash plate type piston pump is controlled to be substantially constant even if a load pressure of the hydraulic actuator changes. This suppresses a rotational fluctuation of the engine.
JP2001-3853A and JP2002-202063A disclose a swash plate type piston pump provided with control pins (control piston, tilting actuator) which operate according to a load pressure, and configured to tilt a swash plate by these control pins.